* {
    margin: 0;
    padding: 0;
    list-style: none;
    box-sizing: border-box;
}
html,
body {
    width: 100%;
    height: 100%;
}

#root {
    width: 100%;
    height: 100%;
    overflow: hidden;
    position: absolute;
    display: flex;
    flex-direction: column;
    .header {
        line-height: 46px;
        height: 45px;
        background: skyblue;
        text-align: center;
        line-height: 46px;
    }
    .main {
       flex: 1;
    }
    .footer {
        line-height: 46px;
        height: 45px;
        background: tomato;
        text-align: center;
        line-height: 46px;
    }
}
